Physical Science

Review One: Physics

VELOCITY

DISTANCETIMEVELOCITY=

v= 12 m1.5 s

= 8 m/s forward

This snowboarder jumps 12 meters in 1.5 seconds. What is his velocity?

This bullet train is traveling 125 m/s when it begins to slow down. When it is finished slowing down it is only going 88 m/s. If it takes the train 25 seconds to slow down, what is the trains

acceleration?

Acceleration

Acceleration = change in velocitychange in time

Acceleration = Final velocity-initial velocitychange in time

a= Vf - Vi t

a= 88 m/s – 125 m/s25 s

-1.4 m/s2a=

Acceleration: Finding Final Velocity

This bicyclist started at rest and accelerated at a rate of 3 m/s2 for 10 seconds. What is his final velocity?

Vf= (accleration x time) + initial velocity

Vf= (3 m/s2 x 10 s) + 0 m/s

Vf= 30 m/s

Newton’s Laws

Law 1All objects have inertia.

Inertia is the tendency of an object to stay at rest or in motion until a force acts

upon it.An objects inertia is based

on its mass.

Law 2The force that an object is

experiencing is the product of its mass and

acceleration.F=ma

Law 3For every action force there is an equal and

opposite reaction force. The hammer and nail are

pushing on each other with the same force.

GravityAll objects have gravity.

The force of gravity depends on the mass of an object. The more mass the object has,

the more gravity that it has.

Also the distance between two objects will determine how great the force of gravity is on those objects. The greater the distance, the less the gravitational force. The closer they are, the greater the force of gravity.

This golf ball has gravity, but not nearly as much as the Earth does…

Mass, Weight, and Gravity

An object’s mass is different than its weight.

An objects weight is based on how much gravity is pulling on the object. In other words, an object’s weight will change depending on what planet it is on. Weight is measured in Newtons.

An objects mass never changes.Mass is measured in grams or kilograms

Force

Every object will fall at the same acceleration due to gravity: 9.8 m/s2. If this

bowling ball and golf ball are dropped at the same

time, they will hit the ground at the same time. However, the bowling ball

will hit with more force

(F=ma). With what Force do these

objects hit the ground?

0.25 kg

12 kg

Force

Kinds of Forces

nuclear gravitationalelectro-

magnetic

Work

Work = Force x Distance

W=Fd

Work is measured in Joules

Pg. 285 Practice #1-5

PowerPower = Work / Time

P= W/t

Power is measured in Watts

Pg. 287 Practice #1-5

Mechanical Advantage

How easy is the work that you are doing?

MA= input distance / output distance

MA= output force / input force

Simple Machines make work EASIER! You still do the same amount of work, it is just spread out over a longer distance.

Simple Machines

Each rope pulling up against the

weight counts as 1 MA. Anything greater than 1 is

considered “easier work.”

Simple MachinesSteeper ramps have less mechanical advantage than lower ones.

3 feet

3.5 feet

3 feet

7 feet

Simple MachinesMore leverage allows for more Mechanical Advantage. The farther the

distance your effort is from the fulcrum, the easier the work is.

In other words, the longer the handles are on a wheelbarrow, the easier it is to lift the load.Also, the farther away from the hinges the door knob is, the easier it is to open the door.

Energy Transformation

Kinds of Energy

Energy Transformations

lightchemical

chemical mechanical/heat

nuclear

light/heat

Transferring Heat

ConvectionConduction

Radiation

Specific HeatSpecific Heat is the amount of heat energy that a substance can absorb

before it changes temperature. Conductors have a low specific heat, while insulators have a high specific heat. Water has a very high specific

heat, which is why the pool is cold in the middle of summer.

Specific Heat FormulaSpecific Heat = Change in Heat Energy

Mass x Temperature Change

c = _Q m x T Pg. 338 #6

Heat Lost or Gained in a SystemHeat gained or lost = mass x specific heat x temperature change

Q=mc T Pg. 338 #1-3

WavesA wave is a transfer of energy

because of an oscillation (vibration).

The atoms in this light bulb are vibrating and making light waves.

The heads of these bongos are vibrating and

making sound waves.

Waves

Waves

Larger WavelengthLower FrequencyLower Energy

Smaller WavelengthHigher FrequencyHigher Energy

WavesWaves can be mechanical or electromagnetic.

WavesWaves can be transverse or longitudinal.

Sound is a mechanical, longitudinal wave.

LOWER FREQUENCY

HIGHER FREQUENCY

HIGH PITCH

LOW PITCH

LOUD

QUIET

Temperature

Density

Speed of Sound

The speed of sound depends on the temperature and density of the medium.

Light

Light is a transverse, electromagnetic wave. Light travels at 300,000,000 m/s.

(3.0 X108 m/s)

Reflection

Waves bounce off of a barrier.

RefractionWaves change direction slightly when they enter a new medium.

InterferenceWaves affect each others amplitudes.

Diffraction

Waves bend around a barrier.

Electricity and Magnetism

Atoms have electron clouds. Those electrons can cause an object to be magnetic. Also, if the protons and electrons of an

object are out of balance, the object can become charged. Electric charge can move and create electric current. Electric

current is energy that can be useful to people.

Electric Charge

+

- - - -- - -

+ + + +

Electric charge can occur because of contact (conduction) or just by

being close (induction).

Static Electricity vs. Current Electricity+

- - - -- - -

+ + + +

Static electricity is when an electric charge sits on a surface. When the charge moves to equilibrium, it is

called a discharge. Current electricity is a flow or vibration of electric charge over a

distance. This can be a direct current (DC) or an alternating

current (AC).

DC

AC

Current

AC

Current is the flow of electricity. It is measured in Amps (A).

Voltage is the potential electrical energy. It is measured in Volts (V).

Resistance is the resistance to current. It is measured in Ohms (O).

Waterfall example

Circuits

Series CircuitParallel Circuit

If one goes out, they all go out.

If one goes out, the others may stay

on (as long as there is a complete circuit

from one end of the battery to the other).

Calculating Voltage

V=IR

Voltage = Current X Resistance

Volts = Amps X Ohms

Yellow Book Pg. 443 #3

MagnetismMagnets have a magnetic field around them. The positive field is a “push”

field, and the negative is a “pull” field. Opposite fields attract, and like fields repel.

Electromagnetism

Electric current sent around a metal object can make the object

become an electromagnet.

The “right hand rule” can be used to determine the

direction of the electric field.

Electromagnetism

If spinning magnets are used to make electric current, it is called a generator.

If electric current is used to make

magnets spin, it is called an

electromotor.

The basic set-up for a generator or electromotor.

Electromagnetism

Electric power plants use generators to make alternating

current (AC). The trick is to get the magnets to

spin (turbines). Steam works well, but making water boil is also tricky,

because burning coal makes pollution. Radioactive material can also heat up water (nuclear

power), but radiation is dangerous. Falling water also does

the trick (hydroelectric), but you have to have the right

environment for falling water.